Jun 9, 2011 2000 UTC Day 1 Convective Outlook | |
Updated: Thu Jun 9 20:04:10 UTC 2011 | |
Probabilistic to Categorical Outlook Conversion Table | |
Public Severe Weather Outlook | |
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The SPC is forecasting ...severe thunderstorms expected over parts of the northeast us this afternoon.... Please read the latest public statement about this event. |
Categorical Graphic |
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Probabilistic Tornado Graphic |
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
Probabilistic Damaging Wind Graphic |
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. |
Probabilistic Large Hail Graphic |
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
SPC AC 092000 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0300 PM CDT THU JUN 09 2011 VALID 092000Z - 101200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF PA/NY/NJ/NH/CT/RI/MA/VT... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHERN PLAINS/MIDWEST TO NEW ENGLAND... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS EASTERN WY/FAR NORTHEAST CO... ...NORTHEAST STATES/NEW ENGLAND... BANDS OF INTENSE THUNDERSTORMS CONTINUE TO MERGE/EXPAND AND GROW UPSCALE THIS AFTERNOON WITH A BROAD/WELL-ORGANIZED LINE OF TSTMS NOW EVOLVING ACROSS THE NORTHEAST STATES/SOUTHERN NEW ENGLAND. SPECIAL 16Z/18Z OBSERVED SOUNDINGS REFLECT VERY STRONG INSTABILITY/STEEP LAPSE RATES ON THE SOUTHERN FRINGE OF STRONG WESTERLIES ALOFT. SCENARIO STILL EXPECTED TO YIELD WIDESPREAD WIND DAMAGE IN ADDITION TO BOUTS OF LARGE HAIL AND PERHAPS A BRIEF TORNADO OR TWO. GIVEN AMPLE PRE-CONVECTIVE LINE HEATING/SOUTHWESTERLY FLOW...THE PRIMARY 20Z CHANGE WAS TO EXTEND THE MODERATE RISK EASTWARD ACROSS VIRTUALLY ALL OF THE SOUTHERN NEW ENGLAND COAST. PLEASE REFERENCE ONGOING/SUBSEQUENT WATCHES AND MESOSCALE DISCUSSIONS. ...LOWER/MIDDLE MO VALLEY AND MIDWEST/SOUTH-CENTRAL PLAINS... PRIOR REASONING GENERALLY HOLDS...ALTHOUGH INTRODUCED SOMEWHAT HIGHER TORNADO PROBABILITIES /10 PERCENT/ IN GENERAL VICINITY OF AN OUTFLOW-AIDED TRIPLE POINT ACROSS THE LOWER-MIDDLE MO VALLEY. REFERENCE MESOSCALE DISCUSSION 1155. ANOTHER CHANGE WAS TO EXTEND THE SLIGHT RISK SOUTHWESTWARD IN VICINITY OF THE DRYLINE ACROSS FAR SOUTHWEST OK INTO PORTIONS OF THE EASTERN TX PANHANDLE/NORTHWEST TX. HERE...DAMAGING WINDS/SOME HAIL MAY BE A CONCERN LATE THIS AFTERNOON/EARLY EVENING. ..GUYER.. 06/09/2011 .PREV DISCUSSION... /ISSUED 1129 AM CDT THU JUN 09 2011/ ...SYNOPSIS... SUPPRESSION OF THE S CENTRAL AND SERN U.S. UPPER RIDGE IS FORECAST TO CONTINUE TODAY...AS THE WRN U.S. TROUGH SHIFTS EWD AND AT THE SAME TIME AN ERN CANADA TROUGH MOVES EWD -- FORCING FALLING HEIGHTS/CYCLONIC FLOW TO SPREAD ACROSS THE NORTHEAST CONUS. AT THE SURFACE...COLD FRONT WILL CONTINUE CROSSING THE ST. LAWRENCE VALLEY/LOWER GREAT LAKES REGION THIS MORNING...AND WILL BECOME A FOCUS FOR WIDESPREAD SEVERE STORM DEVELOPMENT AS IT SHIFTS INTO NEW ENGLAND/NY/PA. THE OUTFLOW-REINFORCED FRONT WILL LINGER WWD ACROSS THE OH VALLEY...AND WILL RETREAT NWD WITH TIME ACROSS THE MO VALLEY REGION WITH FRONTAL LOW DEVELOPMENT EXPECTED IN THIS AREA IN RESPONSE TO EJECTING PIECES OF THE WRN U.S. TROUGH. ...NEW ENGLAND WSWWD ACROSS THE MIDWEST/OH VALLEY... POTENTIALLY WIDESPREAD/DAMAGING WIND EVENT IS FORECAST ACROSS THE NORTHEAST U.S. TODAY. ONGOING CONVECTION ACROSS THIS RISK AREA HAS DIMINISHED EARLY THIS MORNING...WITH CONVECTIVE-COOLED AIR OVER SRN NEW ENGLAND EXPECTED TO CONTINUE RECOVERING. AS A LARGE PLUME OF VERY STEEP LAPSE RATES ATOP A VERY MOIST /NEAR 70 DEWPOINTS/ BOUNDARY LAYER COMBINES WITH CLEARING SKIES SUPPORTING STRONG WARM SECTOR HEATING...MIXED-LAYER CAPE OF 2000 TO 3000 J/KG IS EXPECTED TO DEVELOP QUICKLY THROUGH EARLY AFTERNOON. AN OUTFLOW BOUNDARY INVOF THE MID AND UPPER OH VALLEY -- AND THE COLD FRONT NOW CROSSING THE LOWER GREAT LAKES/ST. LAWRENCE VALLEY -- WILL BECOME THE FOCUS FOR WIDESPREAD STORM DEVELOPMENT OVER THE NEXT COUPLE OF HOURS...SHIFTING SEWD WITH TIME ACROSS NY/PA/OH AND MUCH OF NEW ENGLAND. WITH STRONGEST DEEP-LAYER WLYS PROGGED TO REMAIN N OF THE MASON/DIXON LINE...MOST WIDESPREAD SEVERE THREAT APPEARS TO EXIST FROM SWRN PA ENEWD ACROSS SRN AND ERN NY INTO SRN NEW ENGLAND. HERE...VERY LARGE HAIL THREAT WITH INITIAL SUPERCELL STORMS SHOULD EVOLVE INTO MORE OF A DAMAGING WIND THREAT AS CONVECTION EVOLVES INTO ONE OR MORE BOWING LINES WHICH WILL MOVE QUICKLY EWD. A COUPLE OF TORNADOES MAY ALSO OCCUR -- PARTICULARLY EARLY ON WITH MORE ISOLATED STORMS. BY THIS EVENING...CONVECTION WILL HAVE SHIFTED WELL SEWD...FROM SRN AND ERN NEW ENGLAND WSWWD INTO NRN VA/WV. WITH WEAKER FLOW S OF THE MASON/DIXON LINE...MORE ISOLATED SEVERE POTENTIAL IS FORECAST. ...MID MO VALLEY REGION AND VICINITY SWWD INTO NRN OK... COMPLEX SCENARIO EXISTS ACROSS THE CENTRAL PLAINS/MID MO VALLEY REGION...AS EARLY MORNING SHORT-WAVE RIDGING ALOFT IS FORECAST TO CONTINUE WEAKENING AS TROUGHING SHIFTS ENEWD. AS SURFACE LOW REDEVELOPS NWD INTO THE MID MO VALLEY REGION IN RESPONSE TO THE APPROACHING TROUGH...AND THE SURFACE FRONT OVER NRN MO RETREATS NWD INTO IA...STORM DEVELOPMENT WILL OCCUR -- SUPPORTED BY MODERATE TO STRONG WARM SECTOR DESTABILIZATION. WITH BACKING/STRENGTHENING LOW-LEVEL FLOW INVOF THE DEVELOPING LOW/WARM FRONT BENEATH 50 KT SWLYS AT MID LEVELS SPREADING ATOP THIS AREA...SHEAR/INSTABILITY COMBINATION WILL BE QUITE SUPPORTIVE OF SUPERCELLS. ALONG WITH THREAT FOR VERY LARGE HAIL...ISOLATED TORNADOES WILL ALSO BE POSSIBLE -- MAINLY FROM SERN NEB/NERN KS EWD INTO NRN MO/SRN IA. LOCALLY DAMAGING WINDS WILL ALSO BE POSSIBLE...POSSIBLY BECOMING MORE LIKELY WITH TIME AS SOME CLUSTERING OF CONVECTION OCCURS INTO THE EVENING HOURS. MORE ISOLATED STORM DEVELOPMENT IS FORECAST TO OCCUR SWD ACROSS CENTRAL/ERN KS AND INTO OK...NEAR AND AHEAD OF THE SURFACE COLD FRONT. ALONG WITH POTENTIAL FOR HAIL...DEEP/DRY SUB-CLOUD MIXED LAYER WILL SUPPORT EVAPORATIVELY-ENHANCED DOWNDRAFTS -- AND THUS SOME LIKELIHOOD FOR LOCALLY DAMAGING GUSTS. ...ERN WY AND VICINITY... DESPITE FAIRLY EXTENSIVE MORNING CLOUD COVER...SOME DESTABILIZATION WILL SUPPORT AFTERNOON STORM DEVELOPMENT -- INITIALLY OVER THE HIGHER TERRAIN BUT THEN SPREADING EWD INTO LOWER ELEVATIONS. WITH STRONG /50 TO 60 KT/ MID-LEVEL WLY JET STREAK SHIFTING ACROSS THIS REGION...SHEAR WILL SUPPORT ORGANIZED/SUPERCELL STORMS...AND THUS -- DESPITE POSSIBLY LIMITED INSTABILITY IN PARTS OF THE AREA -- CONTINUATION OF SLIGHT RISK FOR HAIL IS WARRANTED. MORE ISOLATED THREAT APPEARS TO EXTEND SWD INTO THE CO FRONT RANGE AREA...AS SUBSIDENCE EVIDENT IN THE WAKE OF A SEPARATE/DEPARTING SHORT-WAVE TROUGH SHOULD LIMIT COVERAGE A BIT WITH SWD EXTENT. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z